2010 t800 ac not cooling while driving

[jay peacher]

i have a 2010 T800 KW that is not cooling sufficiently while driving down the highway. Mechanic has replaced all of the components in the system, vacumed for 1 hour and charged with 54oz of 134. it works perfectly while in the shop. As you travel down the hghway it will intermittantly cool. When i say all components i mean everything except one hose. Any thoughts?

[bohica2xo]

Does the vent air flow stay the same when it stops cooling, or does the airflow from the vents decrease when it stops cooling?

Given that a truck that old should have about 550,000 miles on it by now, it could be electrical or the refrigeration loop.